Alternating Wedge WRRO Layout for Disk Drive Head Positioning
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Solution Overview
Problem
Conventional disk drives face issues with repeatable runout (RRO) errors due to eccentric tracks, which affect the accuracy of head positioning, leading to data integrity problems and limited storage capacity.
Innovation Solution
The implementation of an alternating wedge repeatable runout (WRRO) layout with wider WRRO fields and shared preambles, allowing for improved off-track read capability and increased storage capacity by optimizing the placement and width of WRRO fields across the disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional WRRO layout is used, then servo overhead is reduced, but off-track read capability and storage capacity are limited
Solution Approach 1:
The patent segments the disk surface into alternating servo wedges, where odd-numbered wedges contain WRRO fields for read compensation and even-numbered wedges contain WRRO fields for write compensation. This segmentation allows different tracks to be served by different wedge sets, improving off-track read capability while distributing the servo overhead across multiple wedges rather than concentrating it in a single location.
Solution Approach 2:
The patent applies local quality by providing track-specific WRRO compensation values in alternating wedges. Each track receives compensation values tailored to its specific RRO characteristics, allowing optimized head positioning for each track individually. This localized approach improves read capability for tracks in alternating wedges without requiring system-wide servo overhead increases.
2Quantity of substance
If WRRO fields are made wider to improve off-track read capability, then storage capacity is increased, but head positioning accuracy may be compromised
Solution Approach 1:
The patent segments head positioning into multiple alternating wedge regions, each with its own WRRO compensation values. This allows the head to be positioned accurately for tracks in odd wedges using odd wedge compensation values, and accurately for tracks in even wedges using even wedge compensation values. The segmentation enables wider effective WRRO fields without compromising positioning accuracy, as each segment maintains its own precision standards.
Solution Approach 2:
The patent implements feedback through the read-compensation mechanism. By reading WRRO compensation values from alternating wedges and using them to adjust head positioning, the system continuously refines positioning accuracy. This feedback loop allows wider WRRO fields to be used while maintaining precision, as the system adapts to actual track conditions based on the compensation values read from the alternating wedges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the accuracy of head positioning and data integrity by increasing the width of WRRO fields, thereby improving the off-track read capability and storage capacity of disk drives, while maintaining data integrity and reducing servo overhead.
Implementation Method 1
The servo information may include a pattern of alternating magnetic transitions (servo burst), which can be read from the disk by the head
Implementation Method 2
The head may be connected to a distal end of an actuator arm that is rotated about a pivot to position the head radially over the disk
Implementation Method 3
A disk drive comprises a rotating disk and a head actuated over the disk
Data Source
AI summary
A disk drive is disclosed comprising a disk, a head actuated over the disk, and a controller. The disk comprises a plurality of data tracks and a plurality of servo wedges, wherein each servo wedge comprises a plurality of wedge repeatable runout (WRRO) fields in a circumferential direction, each of the plurality of WRRO fields including an WRRO compensation value for a different one of the data tracks and having a width that is wider than a width of the respective data track in a radial direction. The controller is configured to read the WRRO compensation value in at least one of the WRRO fields from the disk using the head, and to adjust a position of the head based on the read WRRO compensation value.